What is the role of lab studies in the evaluation of atopic dermatitis (eczema)?

Updated: Aug 02, 2019
  • Author: Brian S Kim, MD, MTR, FAAD; Chief Editor: William D James, MD  more...
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No biomarker for the diagnosis of atopic dermatitis (AD) is known. Laboratory testing is seldom necessary.

A swab of infected skin may help with the isolation of a specific organism (eg, Staphylococcus or Streptococcus) and antibiotic sensitivity. Allergy and radioallergosorbent testing is of little value.

A swab for viral polymerase chain reaction (PCR) may help identify superinfection with herpes simplex virus and identify a diagnosis of eczema herpeticum.

A complete blood cell count for thrombocytopenia helps exclude Wiskott-Aldrich syndrome, and testing to rule out other immunodeficiencies may be helpful. This also helps identify peripheral eosinophilia, which may help to support the diagnosis.

A serum IgE level can be helpful to support the diagnosis.

Scraping to exclude tinea corporis is occasionally helpful.

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